/**
 * accounting-view.js — Phase 1, read-only
 *
 * Drei Bereiche:
 *   1) Accounts Overview — Cards mit Bank- und Credit-Card-Balances
 *   2) Register          — read-only Liste der Transaktionen für ein Konto
 *   3) Reports           — Profit & Loss + Balance Sheet
 */

import { formatDate } from '../utils/helpers.js';

// ────────────────────────────────────────────────────────────────────
// State (modul-lokal)
// ────────────────────────────────────────────────────────────────────

let allAccounts = [];          // alle aktiven Accounts (gesamt, für Dropdown)
let registerAccountId = null;  // aktuell ausgewählter Account fürs Register
let registerStartDate = null;
let registerEndDate = null;

// Reports
let plStartDate = null;
let plEndDate = null;
let plAccountingMethod = 'Accrual';

let bsAsOfDate = null;
let bsAccountingMethod = 'Accrual';

// ────────────────────────────────────────────────────────────────────
// Helpers
// ────────────────────────────────────────────────────────────────────

function fmtMoney(n) {
    if (n == null || isNaN(n)) return '';
    return n.toLocaleString('en-US', {
        style: 'currency',
        currency: 'USD',
        minimumFractionDigits: 2,
        maximumFractionDigits: 2
    });
}

function todayISO() {
    return new Date().toISOString().split('T')[0];
}

function firstOfMonthISO() {
    const d = new Date();
    return new Date(d.getFullYear(), d.getMonth(), 1).toISOString().split('T')[0];
}

function firstOfYearISO() {
    const d = new Date();
    return new Date(d.getFullYear(), 0, 1).toISOString().split('T')[0];
}

function escapeHtml(s) {
    if (s == null) return '';
    return String(s)
        .replace(/&/g, '&')
        .replace(/</g, '&lt;')
        .replace(/>/g, '&gt;')
        .replace(/"/g, '&quot;')
        .replace(/'/g, '&#39;');
}

function showError(slotId, message) {
    const el = document.getElementById(slotId);
    if (!el) return;
    el.innerHTML = `
        <div class="p-4 bg-red-50 border border-red-200 rounded-lg">
            <p class="font-semibold text-red-800">QBO Error</p>
            <p class="text-sm text-red-600 mt-1">${escapeHtml(message)}</p>
        </div>`;
}

function showLoading(slotId, message = 'Loading…') {
    const el = document.getElementById(slotId);
    if (!el) return;
    el.innerHTML = `
        <div class="flex items-center gap-3 p-4 text-gray-500">
            <svg class="animate-spin h-5 w-5 text-blue-600" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
                <circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
                <path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4z"></path>
            </svg>
            <span>${escapeHtml(message)}</span>
        </div>`;
}

// ────────────────────────────────────────────────────────────────────
// Toolbar (top-of-tab heading + sync button)
// ────────────────────────────────────────────────────────────────────

export function injectToolbar() {
    const c = document.getElementById('accounting-toolbar');
    if (!c) return;
    c.innerHTML = `
        <div class="flex items-center gap-3 mb-4 p-4 bg-white rounded-lg shadow-sm border border-gray-200">
            <h2 class="text-lg font-semibold text-gray-800">Accounting</h2>
            <span class="text-sm text-gray-400">read-only</span>
            <div class="ml-auto flex items-center gap-2">
                <button onclick="window.accountingView.refreshAll()"
                    class="px-3 py-1.5 bg-blue-600 text-white rounded-md text-sm font-medium hover:bg-blue-700">
                    ↻ Refresh
                </button>
            </div>
        </div>`;
}

// ────────────────────────────────────────────────────────────────────
// Accounts Overview
// ────────────────────────────────────────────────────────────────────

export async function loadAccountsOverview() {
    const slot = 'accounting-accounts';
    showLoading(slot, 'Loading accounts from QBO…');

    try {
        // Wir laden alle aktiven Accounts in einem Rutsch und filtern client-seitig.
        const accounts = await window.API.accounting.getAccounts(null, true);

        if (accounts.error) {
            showError(slot, accounts.error);
            return;
        }

        allAccounts = accounts;

        // Bank/Credit Card Cards rendern
        const cards = accounts.filter(a =>
            a.accountType === 'Bank' || a.accountType === 'Credit Card'
        );

        const el = document.getElementById(slot);
        if (!cards.length) {
            el.innerHTML = `
                <div class="p-4 bg-gray-50 border border-gray-200 rounded-lg text-gray-600">
                    No bank or credit card accounts found in QBO.
                </div>`;
        } else {
            el.innerHTML = `
                <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4">
                    ${cards.map(a => renderAccountCard(a)).join('')}
                </div>`;
        }

        // Register-Dropdown füttern (nur Bank + Credit Card)
        populateRegisterAccountDropdown(cards);

    } catch (err) {
        console.error('Accounts load failed:', err);
        showError(slot, err.message || 'Failed to load accounts');
    }
}

function renderAccountCard(a) {
    const isBank = a.accountType === 'Bank';
    const accent = isBank ? 'border-blue-200 bg-blue-50' : 'border-purple-200 bg-purple-50';
    const label  = isBank ? 'Bank' : 'Credit Card';
    const labelColor = isBank ? 'text-blue-700' : 'text-purple-700';
    const bal = a.currentBalance;
    const balText = bal != null ? fmtMoney(bal) : '—';
    // Bei Credit Cards ist ein positiver CurrentBalance i.d.R. eine Schuld; nur Hinweis, keine Vorzeichenakrobatik.
    return `
        <div class="rounded-lg border ${accent} p-4 cursor-pointer hover:shadow-md transition"
             onclick="window.accountingView.selectRegisterAccount('${a.id}')">
            <div class="flex items-center justify-between mb-1">
                <span class="text-xs font-semibold uppercase tracking-wide ${labelColor}">${label}</span>
                <span class="text-xs text-gray-400">#${a.id}</span>
            </div>
            <div class="text-base font-semibold text-gray-900 mb-2">${escapeHtml(a.name)}</div>
            <div class="text-2xl font-bold text-gray-900">${balText}</div>
            ${a.accountSubType ? `<div class="text-xs text-gray-500 mt-1">${escapeHtml(a.accountSubType)}</div>` : ''}
        </div>
    `;
}

// ────────────────────────────────────────────────────────────────────
// Register
// ────────────────────────────────────────────────────────────────────

function populateRegisterAccountDropdown(bankCardAccounts) {
    const sel = document.getElementById('reg-account');
    if (!sel) return;

    const current = registerAccountId || sel.value;
    sel.innerHTML = `<option value="">— Select account —</option>` +
        bankCardAccounts.map(a =>
            `<option value="${a.id}">${escapeHtml(a.name)} (${a.accountType})</option>`
        ).join('');

    if (current && bankCardAccounts.find(a => a.id === current)) {
        sel.value = current;
    }
}

export function injectRegisterControls() {
    const c = document.getElementById('accounting-register-controls');
    if (!c) return;

    if (!registerStartDate) registerStartDate = firstOfMonthISO();
    if (!registerEndDate)   registerEndDate   = todayISO();

    c.innerHTML = `
        <div class="flex flex-wrap items-end gap-3 mb-3 p-4 bg-white rounded-lg shadow-sm border border-gray-200">
            <div>
                <label class="block text-xs font-medium text-gray-700 mb-1">Account</label>
                <select id="reg-account" class="px-3 py-1.5 border border-gray-300 rounded-md text-sm w-72">
                    <option value="">— Loading accounts —</option>
                </select>
            </div>
            <div>
                <label class="block text-xs font-medium text-gray-700 mb-1">Start Date</label>
                <input type="date" id="reg-start" value="${registerStartDate}"
                       class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
            </div>
            <div>
                <label class="block text-xs font-medium text-gray-700 mb-1">End Date</label>
                <input type="date" id="reg-end" value="${registerEndDate}"
                       class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
            </div>
            <button onclick="window.accountingView.loadRegister()"
                    class="px-4 py-1.5 bg-blue-600 text-white rounded-md text-sm font-medium hover:bg-blue-700">
                Load Register
            </button>
        </div>
        <div id="accounting-register-table"></div>`;
}

export function selectRegisterAccount(accountId) {
    registerAccountId = accountId;
    const sel = document.getElementById('reg-account');
    if (sel) sel.value = accountId;
    loadRegister();
}

export async function loadRegister() {
    const sel   = document.getElementById('reg-account');
    const start = document.getElementById('reg-start');
    const end   = document.getElementById('reg-end');

    if (!sel || !sel.value) {
        const slot = document.getElementById('accounting-register-table');
        if (slot) slot.innerHTML = `<p class="text-sm text-gray-500 px-4 py-3">Select an account to view the register.</p>`;
        return;
    }

    registerAccountId = sel.value;
    registerStartDate = start.value;
    registerEndDate   = end.value;

    const slot = 'accounting-register-table';
    showLoading(slot, 'Loading register from QBO…');

    try {
        const result = await window.API.accounting.getRegister(
            registerAccountId, registerStartDate, registerEndDate
        );

        if (result.error) {
            showError(slot, result.error);
            return;
        }

        renderRegisterTable(result);
    } catch (err) {
        console.error('Register load failed:', err);
        showError(slot, err.message || 'Failed to load register');
    }
}

function renderRegisterTable(result) {
    const el = document.getElementById('accounting-register-table');
    if (!el) return;

    const rows = result.rows || [];
    const meta = result.meta || {};

    if (!rows.length) {
        el.innerHTML = `
            <div class="p-4 bg-gray-50 border border-gray-200 rounded-lg text-gray-600">
                No transactions in selected range.
            </div>`;
        return;
    }

    const tbody = rows.map(r => `
        <tr class="border-t hover:bg-gray-50">
            <td class="px-3 py-2 text-sm whitespace-nowrap">${escapeHtml(r.date || '')}</td>
            <td class="px-3 py-2 text-sm">${escapeHtml(r.type || '')}</td>
            <td class="px-3 py-2 text-sm">${escapeHtml(r.docNum || '')}</td>
            <td class="px-3 py-2 text-sm">${escapeHtml(r.payee || '')}</td>
            <td class="px-3 py-2 text-sm text-gray-600">${escapeHtml(r.splitAccount || '')}</td>
            <td class="px-3 py-2 text-sm text-gray-500" title="${escapeHtml(r.memo || '')}">${escapeHtml((r.memo || '').slice(0, 60))}</td>
            <td class="px-3 py-2 text-sm text-right whitespace-nowrap ${r.amount < 0 ? 'text-red-600' : 'text-gray-900'}">
                ${r.amount != null ? fmtMoney(r.amount) : ''}
            </td>
        </tr>
    `).join('');

    el.innerHTML = `
        <div class="bg-white rounded-lg shadow-sm border border-gray-200 overflow-hidden">
            <div class="px-4 py-2 border-b bg-gray-50 text-xs text-gray-500">
                ${escapeHtml(meta.reportName || 'Transaction List')}
                ${meta.startPeriod ? '— ' + escapeHtml(meta.startPeriod) : ''}
                ${meta.endPeriod ? ' to ' + escapeHtml(meta.endPeriod) : ''}
                · ${rows.length} rows
            </div>
            <div class="overflow-x-auto">
                <table class="min-w-full text-sm">
                    <thead class="bg-gray-50">
                        <tr>
                            <th class="px-3 py-2 text-left font-medium text-gray-700">Date</th>
                            <th class="px-3 py-2 text-left font-medium text-gray-700">Type</th>
                            <th class="px-3 py-2 text-left font-medium text-gray-700">No.</th>
                            <th class="px-3 py-2 text-left font-medium text-gray-700">Payee</th>
                            <th class="px-3 py-2 text-left font-medium text-gray-700">Split / Category</th>
                            <th class="px-3 py-2 text-left font-medium text-gray-700">Memo</th>
                            <th class="px-3 py-2 text-right font-medium text-gray-700">Amount</th>
                        </tr>
                    </thead>
                    <tbody>${tbody}</tbody>
                </table>
            </div>
        </div>`;
}

// ────────────────────────────────────────────────────────────────────
// Reports — P&L + Balance Sheet
// ────────────────────────────────────────────────────────────────────

export function injectReportsControls() {
    const c = document.getElementById('accounting-reports');
    if (!c) return;

    if (!plStartDate) plStartDate = firstOfYearISO();
    if (!plEndDate)   plEndDate   = todayISO();
    if (!bsAsOfDate)  bsAsOfDate  = todayISO();

    c.innerHTML = `
        <div class="grid grid-cols-1 lg:grid-cols-2 gap-4">
            <!-- P&L -->
            <div class="bg-white rounded-lg shadow-sm border border-gray-200">
                <div class="px-4 py-3 border-b bg-gray-50">
                    <h3 class="font-semibold text-gray-800">Profit &amp; Loss</h3>
                </div>
                <div class="p-4">
                    <div class="flex flex-wrap items-end gap-3 mb-3">
                        <div>
                            <label class="block text-xs font-medium text-gray-700 mb-1">Start</label>
                            <input type="date" id="pl-start" value="${plStartDate}"
                                   class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
                        </div>
                        <div>
                            <label class="block text-xs font-medium text-gray-700 mb-1">End</label>
                            <input type="date" id="pl-end" value="${plEndDate}"
                                   class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
                        </div>
                        <div>
                            <label class="block text-xs font-medium text-gray-700 mb-1">Method</label>
                            <select id="pl-method" class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
                                <option value="Accrual" ${plAccountingMethod === 'Accrual' ? 'selected' : ''}>Accrual</option>
                                <option value="Cash" ${plAccountingMethod === 'Cash' ? 'selected' : ''}>Cash</option>
                            </select>
                        </div>
                        <button onclick="window.accountingView.loadProfitLoss()"
                                class="px-3 py-1.5 bg-blue-600 text-white rounded-md text-sm font-medium hover:bg-blue-700">
                            Run
                        </button>
                    </div>
                    <div id="pl-result"></div>
                </div>
            </div>

            <!-- Balance Sheet -->
            <div class="bg-white rounded-lg shadow-sm border border-gray-200">
                <div class="px-4 py-3 border-b bg-gray-50">
                    <h3 class="font-semibold text-gray-800">Balance Sheet</h3>
                </div>
                <div class="p-4">
                    <div class="flex flex-wrap items-end gap-3 mb-3">
                        <div>
                            <label class="block text-xs font-medium text-gray-700 mb-1">As of</label>
                            <input type="date" id="bs-asof" value="${bsAsOfDate}"
                                   class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
                        </div>
                        <div>
                            <label class="block text-xs font-medium text-gray-700 mb-1">Method</label>
                            <select id="bs-method" class="px-3 py-1.5 border border-gray-300 rounded-md text-sm">
                                <option value="Accrual" ${bsAccountingMethod === 'Accrual' ? 'selected' : ''}>Accrual</option>
                                <option value="Cash" ${bsAccountingMethod === 'Cash' ? 'selected' : ''}>Cash</option>
                            </select>
                        </div>
                        <button onclick="window.accountingView.loadBalanceSheet()"
                                class="px-3 py-1.5 bg-blue-600 text-white rounded-md text-sm font-medium hover:bg-blue-700">
                            Run
                        </button>
                    </div>
                    <div id="bs-result"></div>
                </div>
            </div>
        </div>`;
}

export async function loadProfitLoss() {
    plStartDate = document.getElementById('pl-start').value;
    plEndDate   = document.getElementById('pl-end').value;
    plAccountingMethod = document.getElementById('pl-method').value;

    showLoading('pl-result', 'Loading P&L from QBO…');
    try {
        const data = await window.API.accounting.getProfitAndLoss(
            plStartDate, plEndDate, plAccountingMethod
        );
        if (data.error) return showError('pl-result', data.error);
        document.getElementById('pl-result').innerHTML = renderQboReport(data);
    } catch (err) {
        showError('pl-result', err.message || 'Failed to load P&L');
    }
}

export async function loadBalanceSheet() {
    bsAsOfDate = document.getElementById('bs-asof').value;
    bsAccountingMethod = document.getElementById('bs-method').value;

    showLoading('bs-result', 'Loading Balance Sheet from QBO…');
    try {
        const data = await window.API.accounting.getBalanceSheet(
            bsAsOfDate, bsAccountingMethod
        );
        if (data.error) return showError('bs-result', data.error);
        document.getElementById('bs-result').innerHTML = renderQboReport(data);
    } catch (err) {
        showError('bs-result', err.message || 'Failed to load Balance Sheet');
    }
}

// ────────────────────────────────────────────────────────────────────
// Generic QBO Report Renderer (P&L + Balance Sheet)
// QBO Reports haben rekursive Section/Row-Bäume mit Summary-Zeilen.
// Wir rendern sie als verschachtelte HTML-Tabelle.
// ────────────────────────────────────────────────────────────────────

function renderQboReport(report) {
    if (!report || !report.Header) {
        return `<p class="text-sm text-gray-500">No report data.</p>`;
    }

    const cols = (report.Columns && report.Columns.Column) || [];
    const colCount = cols.length;

    let body = '';
    if (report.Rows && report.Rows.Row) {
        body = renderReportRows(report.Rows.Row, 0, colCount);
    }

    const headerRow = cols.map(c =>
        `<th class="px-3 py-2 text-right font-medium text-gray-700 first:text-left">${escapeHtml(c.ColTitle || '')}</th>`
    ).join('');

    return `
        <div class="text-xs text-gray-500 mb-2">
            ${escapeHtml(report.Header.ReportName || '')}
            ${report.Header.StartPeriod ? '· ' + escapeHtml(report.Header.StartPeriod) + ' – ' + escapeHtml(report.Header.EndPeriod) : ''}
            ${report.Header.ReportBasis ? '· ' + escapeHtml(report.Header.ReportBasis) : ''}
        </div>
        <div class="overflow-x-auto border border-gray-200 rounded">
            <table class="min-w-full text-sm">
                <thead class="bg-gray-50 border-b">
                    <tr>${headerRow}</tr>
                </thead>
                <tbody>${body}</tbody>
            </table>
        </div>`;
}

function renderReportRows(rows, depth, colCount) {
    if (!rows) return '';
    const arr = Array.isArray(rows) ? rows : [rows];
    let html = '';

    for (const row of arr) {
        const isSection = row.type === 'Section' || row.Rows || row.Summary;
        const indentPx = depth * 16;

        if (row.Header && row.Header.ColData) {
            // Section header row
            const headerCells = row.Header.ColData.map((c, i) => {
                if (i === 0) {
                    return `<td class="px-3 py-1.5 font-semibold text-gray-800" style="padding-left:${12 + indentPx}px">${escapeHtml(c.value || '')}</td>`;
                }
                return `<td class="px-3 py-1.5 text-right text-gray-500"></td>`;
            }).join('');
            html += `<tr class="bg-gray-50">${headerCells}</tr>`;
        }

        if (isSection && row.Rows && row.Rows.Row) {
            html += renderReportRows(row.Rows.Row, depth + 1, colCount);
        }

        if (row.Summary && row.Summary.ColData) {
            const sumCells = row.Summary.ColData.map((c, i) => {
                if (i === 0) {
                    return `<td class="px-3 py-1.5 font-semibold text-gray-700 border-t" style="padding-left:${12 + indentPx}px">${escapeHtml(c.value || '')}</td>`;
                }
                return `<td class="px-3 py-1.5 text-right font-semibold text-gray-900 border-t">${escapeHtml(c.value || '')}</td>`;
            }).join('');
            html += `<tr>${sumCells}</tr>`;
        }

        if (!isSection && row.ColData) {
            // Plain data row
            const cells = row.ColData.map((c, i) => {
                if (i === 0) {
                    return `<td class="px-3 py-1.5" style="padding-left:${12 + indentPx}px">${escapeHtml(c.value || '')}</td>`;
                }
                return `<td class="px-3 py-1.5 text-right">${escapeHtml(c.value || '')}</td>`;
            }).join('');
            html += `<tr>${cells}</tr>`;
        }
    }

    return html;
}

// ────────────────────────────────────────────────────────────────────
// Init / Public Entry Points
// ────────────────────────────────────────────────────────────────────

export function renderAccountingView() {
    injectToolbar();
    injectRegisterControls();
    injectReportsControls();
    loadAccountsOverview();
}

export function refreshAll() {
    loadAccountsOverview();
    if (registerAccountId) loadRegister();
}

// Expose for onclick handlers
window.accountingView = {
    renderAccountingView,
    refreshAll,
    loadAccountsOverview,
    loadRegister,
    selectRegisterAccount,
    loadProfitLoss,
    loadBalanceSheet
};